US20190101943A1 - Relay Valve and Force Balancing Method - Google Patents
Relay Valve and Force Balancing Method Download PDFInfo
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- US20190101943A1 US20190101943A1 US16/146,379 US201816146379A US2019101943A1 US 20190101943 A1 US20190101943 A1 US 20190101943A1 US 201816146379 A US201816146379 A US 201816146379A US 2019101943 A1 US2019101943 A1 US 2019101943A1
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- 238000010276 construction Methods 0.000 claims description 3
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- 238000004886 process control Methods 0.000 description 6
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- 238000013022 venting Methods 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K31/00—Actuating devices; Operating means; Releasing devices
- F16K31/12—Actuating devices; Operating means; Releasing devices actuated by fluid
- F16K31/126—Actuating devices; Operating means; Releasing devices actuated by fluid the fluid acting on a diaphragm, bellows, or the like
- F16K31/1268—Actuating devices; Operating means; Releasing devices actuated by fluid the fluid acting on a diaphragm, bellows, or the like with a plurality of the diaphragms
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K31/00—Actuating devices; Operating means; Releasing devices
- F16K31/02—Actuating devices; Operating means; Releasing devices electric; magnetic
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D16/00—Control of fluid pressure
- G05D16/20—Control of fluid pressure characterised by the use of electric means
- G05D16/2093—Control of fluid pressure characterised by the use of electric means with combination of electric and non-electric auxiliary power
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
- F15B13/0401—Valve members; Fluid interconnections therefor
- F15B13/0405—Valve members; Fluid interconnections therefor for seat valves, i.e. poppet valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
- F15B13/042—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure
- F15B13/043—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves
- F15B13/0433—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves the pilot valves being pressure control valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K31/00—Actuating devices; Operating means; Releasing devices
- F16K31/12—Actuating devices; Operating means; Releasing devices actuated by fluid
- F16K31/122—Actuating devices; Operating means; Releasing devices actuated by fluid the fluid acting on a piston
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K37/00—Special means in or on valves or other cut-off apparatus for indicating or recording operation thereof, or for enabling an alarm to be given
- F16K37/0025—Electrical or magnetic means
- F16K37/0041—Electrical or magnetic means for measuring valve parameters
Definitions
- the present disclosure generally relates to pneumatic valves and, more particularly, to pneumatic relay valves.
- Relay valves can be utilized in systems to receive an air mass flow, such as from an I/P converter, and, in response, output a larger air mass flow to an actuator.
- This type of relay valve can have an inherent deadtime during operation that corresponds to the time when the I/P converter is first operated and when the larger air mass flow beings to flow out of the relay valve.
- Some actuators require accurate pulses of air out of the relay valve and the inherent deadtime of the system can influence the accuracy of the pluses of air. If the deadtime is not consistent, fine control movements can become erratic.
- One source of variation in the deadtime can come from the areas of the exhaust and supply ports within the relay valve and changes in pressure from the actuator and/or supply.
- the pressure(s), in combination with the areas, apply forces on the valve seats sealing the exhaust and/or supply ports. If these values change due to fluctuating pressures, a different pressure is required from the I/P converter to open the relay valve, which results in a change of deadtime.
- a relay valve in some embodiments, includes a housing with an exhaust chamber, a supply chamber coupled to a supply, an actuator chamber coupled to an actuator, an exhaust port connecting the exhaust chamber to the actuator chamber, a supply port connecting the supply chamber to the actuator chamber, and an I/P chamber coupled to an I/P converter.
- the relay valve further includes a stack having a first end, a second end, and a valve seat portion where the stack is configured to be shifted within the housing to thereby control opening and closing of one of the exhaust port or supply port with the valve seat portion thereof.
- a spring of the relay valve is configured to apply a force on the first end of the stack, while an I/P diaphragm mounted within the housing to extend across the I/P chamber is configured to apply a force on the second end of the stack based on pressure provided by the I/P converter.
- the relay valve further includes an actuator diaphragm mounted within the housing and coupled to the stack where the actuator diaphragm is disposed on an opposite side of the actuator chamber as the one of the exhaust port or supply port and wherein an area of the actuator diaphragm is generally equal to an area of the one of the exhaust port or supply port such that forces acting on the stack due to pressure within the actuator chamber acting on the valve seat portion and the actuator diaphragm cancel one another out.
- the stack can be a supply stack that is configured to be shifted within the housing to thereby control opening and closing of the supply port with the valve seat portion thereof.
- These approaches can further include providing a supply diaphragm mounted within the housing and coupled to the supply stack. where the supply diaphragm is disposed on an opposite side of the supply chamber as the supply port, and where an area of the supply diaphragm is generally equal to an area of the supply port such that forces acting on the supply stack due to pressure within the actuator chamber acting on the valve seat portion and the actuator diaphragm cancel one another out.
- the stack can be an exhaust stack that is configured to be shifted within the housing to thereby control opening and closing of the exhaust port with the valve seat portion thereof.
- These approaches can further include providing a supply stack having a first end, a second end, and a valve seat portion where the supply stack is configured to be shifted within the housing to thereby control opening and closing of the supply port with the valve seat portion thereof.
- the actuator diaphragm can be a first actuator diaphragm
- the I/P diaphragm can be a first I/P diaphragm
- the spring can be a first spring
- the I/P chamber can be an I/P exhaust chamber
- the housing further includes an I/P supply chamber coupled to a supply I/P converter
- the relay valve further includes a second spring configured to apply a force on the first end of the supply stack, a second I/P diaphragm mounted within the housing to extend across the supply I/P chamber, the second I/P diaphragm configured to apply a force on the second end of the supply stack based on pressure provided by the supply I/P converter, and a second actuator diaphragm mounted within the housing and coupled to the supply stack, the second actuator diaphragm disposed on an opposite side of the actuator chamber as the supply port.
- the stack can include an I/P member disposed within the I/P chamber of the housing and a valve rod member having a first end, a second end, and the valve seat portion, where the second end of the valve rod and the I/P member engage one another on either side of the I/P diaphragm.
- a relay valve in some embodiments, includes a housing with an exhaust chamber, a supply chamber coupled to a supply, an actuator chamber coupled to an actuator, an exhaust port connecting the exhaust chamber to the actuator chamber, and a supply port connecting the supply chamber to the actuator chamber.
- the relay valve further includes an exhaust stack having a valve seat portion and being configured to be shifted within the housing to thereby control opening and closing of the exhaust port with the valve seat portion thereof, and a supply stack having a valve seat portion and being configured to be shifted within the housing to thereby control opening and closing of the supply port with the valve seat portion thereof.
- a first actuator diaphragm of the relay valve is mounted within the housing and coupled to the exhaust stack.
- the first actuator diaphragm is disposed on an opposite side of the actuator chamber as the exhaust port and an area of the first actuator diaphragm is generally equal to an area of the exhaust port such that forces acting on the exhaust stack due to pressure within the actuator chamber acting on the valve seat portion and the first actuator diaphragm cancel one another out.
- a second actuator diaphragm of the relay valve is mounted within the housing and coupled to the supply stack.
- the second actuator diaphragm is disposed on an opposite side of the actuator chamber as the supply port and an area of the second actuator diaphragm is generally equal to an area of the supply port such that forces acting on the supply stack due to pressure within the actuator chamber acting on the valve seat portion and the second actuator diaphragm cancel one another out.
- the first actuator diaphragm and the second actuator diaphragm are portions of a single diaphragm.
- the relay valve can further include a supply diaphragm mounted within the housing and coupled to the supply stack where the supply diaphragm is disposed on an opposite side of the supply chamber as the supply port and an area of the supply diaphragm is generally equal to an area of the supply port such that forces acting on the supply stack due to pressure within the supply chamber acting on the valve seat portion and the supply diaphragm cancel one another out.
- the housing can include first and second I/P chambers coupled to first and second I/P converters, second ends of the exhaust and supply stacks being disposed within the first and second I/P chambers.
- the relay valve can further include an I/P diaphragm that includes first and second portions extending across the first and second I/P chambers where the first and second portions are configured to apply a force on the second ends of the exhaust and supply stacks, respectively, based on pressure provided by the respective I/P converter.
- the relay valve can further include a first spring disposed within the housing and configured to apply a force on the first end of the exhaust stack and a second spring disposed within the housing and configured to apply a force on the first end of the supply stack.
- any of the relay valves described herein can be incorporated into a system that includes first and second I/P converters coupled to the relay valve and an actuator coupled to the relay valve.
- the system can further include a controller coupled to the first and second I/P converters and configured to receive feedback from the actuator.
- a method for operating a relay valve is described herein where the relay valve includes a housing including an exhaust chamber, a supply chamber coupled to a supply, an actuator chamber coupled to an actuator, an exhaust port connecting the exhaust chamber to the actuator chamber, a supply port connecting the supply chamber to the actuator chamber, and an I/P chamber coupled to an I/P converter.
- the method includes applying a first force on a first end of a stack disposed within the housing and configured to be shifted therein to thereby control opening and closing of the exhaust port or supply port with a valve seat portion thereof, applying a second force on the valve seat portion of the stack based on pressure within the actuator chamber, applying a third force on the stack having a magnitude generally equal to the second force in an opposite direction thereof with an actuator diaphragm disposed across a portion of the actuator chamber to thereby negate the impact of the second force on the stack, receiving an input pressure from the I/P converter in the I/P chamber, and applying a fourth force on a second end of the stack with an I/P diaphragm disposed across the I/P chamber based on the input pressure to thereby control shifting of the stack.
- the stack is a supply stack configured to be shifted within the housing to thereby control opening and closing of the supply port with the valve seat portion thereof.
- the method can further include applying a fifth force on the valve seat portion of the supply stack based on pressure within the supply chamber and applying a sixth force on the supply stack having a magnitude generally equal to the fifth force in an opposite direction thereof with a supply diaphragm disposed across a portion of the supply chamber to thereby negate the impact of the fifth force on the supply stack.
- the stack is an exhaust stack configured to be shifted within the housing to thereby control opening and closing of the exhaust port with the valve seat portion thereof.
- the I/P chamber can be a first I/P chamber
- the actuator diaphragm can be a first actuator diaphragm
- the housing can further includes a second I/P chamber coupled to a second I/P converter.
- the method can further include applying a first force on a first end of a supply stack disposed within the housing and configured to be shifted therein to thereby control opening and closing of the supply port with a valve seat portion thereof, applying a second force on the valve seat portion of the supply stack based on pressure within the actuator chamber, applying a third force on the supply stack having a magnitude generally equal to the second force in an opposite direction thereof with a second actuator diaphragm disposed across a portion of the actuator chamber to thereby negate the impact of the second force on the supply stack, receiving an input pressure from the second I/P converter in the second I/P chamber, and applying a fourth force on a second end of the supply stack with a second I/P diaphragm disposed across the second I/P chamber based on the input pressure from the second I/P converter to thereby control shifting of the supply stack.
- FIG. 1 is a block diagram of an example implementation of a valve positioning system, including a spring return pneumatic actuator, in accordance with various embodiments of the present disclosure
- FIG. 2 is a block diagram of an alternative implementation of the valve positioning system of FIG. 1 , including a double acting pneumatic actuator, in accordance with various embodiments of the present disclosure
- FIG. 3 is a focused block diagram including a pneumatic relay valve in accordance with various embodiments of the present disclosure
- FIG. 4 is a first embodiment of a relay valve in accordance with various embodiments of the present disclosure.
- FIG. 5 is a force diagram for an exhaust stack of the relay valve of FIG. 4 in accordance with various embodiments of the present disclosure
- FIG. 6 is a force diagram for a supply stack of the relay valve of FIG. 4 in accordance with various embodiments of the present disclosure
- FIG. 7 is a second embodiment of a relay valve in accordance with various embodiments of the present disclosure.
- FIG. 8 is a force diagram for a supply stack of the relay valve of FIG. 7 in accordance with various embodiments of the present disclosure.
- a relay valve configured according to the various embodiments as described herein advantageously provides consistent, reliable start point pressures for both supply and exhaust functionalities.
- the relay valves described herein utilize a plurality of diaphragms to neutralize any variable forces due to pressure in an actuator and, optionally, a supply connected to the relay valve.
- FIG. 1 is a block diagram of an example implementation of a valve positioning system comprising an actuator 1 for opening and closing a process control valve (PCV).
- the actuator 1 may be a spring return pneumatic actuator.
- the positioner 10 may configured to include some or all of the advanced functionality of a digital valve controller (DVC), though FIG. 1 does not illustrate this functionality.
- the actuator 1 may comprise a pneumatic chamber 2 and a spring 3 , which may be separated by a piston 4 . Addition of pneumatic pressure to the pneumatic chamber 2 may cause movement of the piston 4 , which may in turn cause movement of a stem 5 connected to the piston 4 . Conversely, removal of pneumatic pressure from the pneumatic chamber 2 may cause opposite movement of the piston 4 and the stem 5 .
- the movement of the stem 5 e.g., linear or angular displacement of the stem 5
- the process control valve may control fluid flow within a process control system, such as a chemical or other process control plant.
- An supply/exhaust port 6 may supply air or other control fluid to the pneumatic chamber 2 , and/or conversely, may exhaust control fluid from the pneumatic chamber 2 .
- the supply/exhaust port 6 may comprise separate ports for supply and exhaust of control fluid to the pneumatic chamber 2 . Addition or removal of control fluid to the pneumatic chamber 2 may increase or decrease, respectively, the pneumatic pressure in the pneumatic chamber 2 , consequently causing a change in actuator position and thus a change in process fluid flow through the process fluid valve.
- the actuator 1 may additionally include a fail-safe spring (not pictured) in the pneumatic chamber 2 .
- a fail-safe spring (not pictured) in the pneumatic chamber 2 .
- Such a spring may place an actuator at one limit of the actuators range when, for example, the chamber 2 depressurizes due to a control fluid leak.
- a mechanism in an alternative actuator 1 may translate the linear motion of the piston 4 into rotary motion of the stem 5 by means of rack and pinion, scotch yoke, or another mechanism.
- a position sensor 11 may be configured to detect the position of the actuator 1 , for example, by detecting linear displacement of the stem 5 .
- an alternative position sensor 11 may be configured to measure angular displacement of some portion of the alternative rotary actuator.
- a pressure sensor 14 may be configured to detect an amount of pneumatic pressure in the pneumatic chamber 2 .
- the pressure sensor 14 may be located at an outlet port of the chamber 2 .
- the pressure sensor 14 may be integrated into the body of the positioner 10 , and connected to chamber 2 via a pneumatic line.
- the position sensor 11 and pressure sensor 14 may be communicatively connected to a controller 16 to provide feedback of observed actuator position and pressure to the controller 16 .
- the controller 16 may include wired and/or wireless connections, circuitry for communications and signal processing, non-transient memory and/or a human-machine interface.
- the controller 16 includes processing software such as a microprocessor and a computer-readable memory to store software instructions.
- the controller 16 may be configured to receive position feedback from the position sensor 11 , and/or pressure feedback from the pressure sensor 14 .
- the controller 16 may be configured to use the received feedback to execute a control algorithm to control position of the actuator 1 .
- the controller may comprise one or more microprocessors.
- the controller 16 may comprise field programmable gate arrays (FPGAs) or analog circuits.
- the controller 16 may be configured to execute the control algorithm (e.g., a Multiple Input Multiple Output (MIMO) control algorithm) to output electrical control signals to respective current-to-pressure (I/P) transducers 20 a and 20 b for generating pneumatic signals for the actuator 1 .
- the controller 16 may additionally be configured to compute other signals, such as diagnostic information about the positioner and the actuator.
- the positioner 10 may additionally comprise an interface 18 communicatively coupled to the controller 16 .
- the interface 18 may communicate actuator control constraints, process variable set points, and/or other information, that may be defined by a human operator and/or a control algorithm.
- the controller 16 may output electrical signals for controlling the actuator 1 , the electrical signals transmitted to the I/P transducers 20 a and 20 b , which may be connected to a pneumatic relay 24 which may amplify the flow rates specified via the transducers 20 a and 20 b (as will be described further herein, e.g., with regard to FIG. 3 ).
- Electrical signals transmitted to the I/P transducer 20 a may correspond to the supply of pressurized control fluid to the pneumatic chamber 2
- signals transmitted to the transducer 20 b may correspond to exhaust of control fluid from the chamber 2 .
- the pneumatic relay 24 may amplify the pneumatic signals generated via the transducers 20 a and 20 b to supply or exhaust pressure from the pneumatic chamber 2 via the supply/exhaust port 6 .
- FIG. 2 is a block diagram of an alternative implementation of the valve positioning system of FIG. 1 .
- a double-acting pneumatic actuator 1 replaces the spring return pneumatic actuator 1 of FIG. 1 .
- the double-acting pneumatic actuator 1 includes an upper pneumatic chamber 2 and a lower pneumatic chamber 7 .
- the valve positioning system of FIG. 2 may operate similarly to the system described with regard to FIG. 1 , apart the differences described herein.
- the upper pneumatic chamber 2 and lower pneumatic chamber 7 may be separated by the piston 4 .
- a pressure differential between the chambers 2 and 7 may cause movement of the piston 4 , which in turn may cause movement of the stem 5 , thus opening or closing the process control valve and affecting process fluid flow.
- Supply/exhaust ports 6 a and 6 b may supply and/or exhaust control fluid from the upper chamber 2 and lower chamber 7 , respectively. As the amount of control fluid changes in either or both of the chambers 2 and 7 , a control fluid pressure differential in the chambers 2 and 7 may cause positional movement of the piston 4 and stem 5 to partially or fully open or close the control valve. In some embodiments, either or both of the supply/exhaust ports 6 a and 6 b may comprise separate ports for supply and exhaust of control to the respective chambers 2 and 7 .
- the double-acting actuator 1 may include a spring (not shown) in one or both of the chambers 2 and 7 for fail-open or fail-closed action.
- a spring may place an actuator at one limit of the actuators range when, for example, either of the chambers 2 and 7 depressurize due to a leak.
- a pair of pressure sensors 14 a and 14 b may be configured to detect an amount of pneumatic pressure in the upper pneumatic chamber 2 and lower pneumatic chamber 7 , respectively.
- the pressure sensors 14 a and 14 b may be located at outlet ports of the respective chambers 2 and 7 . Additionally or alternatively, the pressure sensors 14 a and 14 b may be integrated into the body of the positioner 10 , and connected to the respective chambers 2 and 7 via pneumatic lines. In any case, the position sensor 11 and pressure sensors 14 a and 14 b may be communicatively connected to the controller 16 to provide feedback of observed actuator position and pressure to the controller 16 .
- the controller 16 may be a similar controller to that described regarding the FIG. 1 implementation.
- the controller 16 may be configured to execute a control algorithm (e.g., a MIMO control algorithm) to output electrical control signals to I/P transducers 20 a - 20 d .
- Electrical signals transmitted to the I/P transducer 20 a may correspond to the supply of pressurized control fluid to the upper pneumatic chamber 2
- signals transmitted to the transducer 20 b may correspond to exhaust of control fluid from the upper chamber 2
- Electrical signals transmitted to the I/P transducer 20 c may correspond to the supply of pressurized control fluid to the lower pneumatic chamber 7
- signals transmitted to the transducer 20 d may correspond to exhaust of control fluid from the lower chamber 7 .
- a pneumatic relay 24 may amplify the pneumatic signals generated via the transducers 20 a and 20 b to supply or exhaust pressure from the upper pneumatic chamber 2 via the supply/exhaust port 6 a .
- a pneumatic relay 24 may amplify the pneumatic signals generated via the transducers 20 c and 20 d to supply or exhaust pressure from the lower pneumatic chamber 7 via the supply/exhaust port 6 b.
- FIG. 3 is a more focused block diagram including a pneumatic relay 24 in accordance with various embodiments of the present disclosure.
- the components illustrated in FIG. 3 may be included, for example, in the valve positioning systems described with regard to FIG. 1 and FIG. 2 .
- An electrical control signal (current 0 may be supplied to the I/P transducer 20 .
- the I/P transducer 20 receives the control signal and outputs a small air mass flow (m i/p ) to the pneumatic relay 24 .
- This small air mass flow may pressurize a diaphragm chamber in the relay 24 , which opens a relay valve in the relay 24 .
- a larger air mass flow (m relay ) may flow from the relay 24 to the actuator 1 (e.g., via a supply/exhaust port of the actuator 1 to pressurize or depressurize a pneumatic chamber of the actuator 1 .
- a deadtime may correspond to a period of time that is present between a first time at which current i is first supplied to the I/P transducer 20 , and a second, subsequent time at which the air mass flow m relay begins to flow out of the pneumatic relay 24 .
- Inconsistent deadtime in a valve positioner may cause fine control movements (e.g., actuator position movements) to become erratic.
- Inconsistency in deadtime may be caused, for example, via an unbalanced area of a supply port and exhaust port of the pneumatic relay, as will be described with regard to FIGS. 4-8 .
- the relay valve 24 in a first form is shown.
- the relay valve 24 includes a housing 202 having an exhaust chamber 204 , a supply chamber 206 , a first I/P chamber 208 , a second I/P chamber 210 , and an actuator chamber 212 .
- the relay valve 24 further includes an I/P diaphragm 214 and an actuator diaphragm 216 .
- the I/P diaphragm 214 divides the first and second I/P chambers 208 , 210 into a vented portion 218 and a pressurized portion 220 .
- the housing 202 has a five piece, multi-part construction including first 222 , second 224 , third 226 , fourth 228 , and fifth 230 portions.
- the first and second portions 222 , 224 define the exhaust and supply chambers 204 , 206 therebetween.
- the second and third portions 224 , 226 define the actuator chamber 212 therebetween and the second portion 224 includes an exhaust port 232 connecting the actuator chamber 212 to the exhaust chamber 204 and a supply port 234 connecting the actuator chamber 212 to the supply chamber 206 .
- the actuator diaphragm 216 is disposed between the third and fourth portions 226 , 228 to thereby seal the actuator chamber 212 .
- the third and fourth portions 226 , 228 define first and second actuator diaphragm chambers 235 , 237 , having first and second portions 239 , 241 of the actuator diaphragm 216 extending thereacross with pressure from the actuator on one side thereof and atmosphere on the other side thereof.
- the chambers 235 , 237 can be generally cylindrical so that the first and second portions 239 , 241 of the actuator diaphragm 216 are generally circular.
- all actuators/actuator portions described herein can be configured as commonly understood with excess material to allow the diaphragm/diaphragm portion to flex in either direction.
- the fourth and fifth portions 228 , 230 define the first and second I/P chambers 208 , 210 and capture the I/P diaphragm 214 therebetween.
- First and second portions 243 , 245 of the I/P diaphragm extend across the first and second I/P chambers 208 , 210 .
- the vented portions 218 of the first and second I/P chambers 208 , 210 are defined by the fourth portion 230 and the I/P diaphragm 214 and the pressurized portions 220 are defined by the fifth portion 230 and the I/P diaphragm 214 .
- the supply chamber 206 is coupled to and receives pressurized gas from a supply 233 via a suitable connection/port 236 .
- the exhaust chamber 204 includes a vent 238 open to atmosphere.
- the vented portions 218 of the first and second I/P chambers 208 , 210 includes vents 240 open to atmosphere and the pressurized portions 220 thereof are coupled to first and second I/P converters 20 a , 20 b , respectively, via suitable passages or ports 242 , to thereby receive pressurized gas and exhaust gas.
- the housing 202 can include cavities or mounts 244 to receive the first and second I/P converters 20 a , 20 b therein.
- the relay valve 24 further includes an exhaust stack 246 that extends from the exhaust chamber 204 , through the exhaust port 232 and the actuator chamber 212 , and to the vented portion 218 of the first I/P chamber 208 through passages 248 , 250 extending from the actuator chamber 212 to the first I/P chamber 208 .
- the exhaust stack 246 includes a cup-shaped member 252 at a first end 254 thereof; an intermediate valve rod 256 having a first end 258 , a narrowed portion 260 extending through the exhaust port 232 , a valve seat portion 262 , and a second end 264 ; and an I/P member 266 having a disc-shaped portion 268 and a rod portion 270 at a second end 272 thereof.
- the first end 254 of the intermediate valve rod 252 is configured to mount or couple to the cup-shaped member 248 , such as by extending into a cavity 274 thereof, and the second end 264 engages the rod portion 270 of the I/P member 266 through the I/P diaphragm 214 .
- the exhaust stack 246 engages a first spring 276 with the first end 254 thereof. So configured, the first spring 276 applies a force on the first end 254 of the exhaust stack 246 .
- the first portion 243 of the I/P diaphragm 214 due to pressure in the first I/P chamber 208 , provides a counter force to the second end 272 thereof.
- controlling the pressure in the I/P chamber 208 to apply a larger force on the second end 272 than the spring force causes an annular seat member 278 of the valve seat portion 262 to engage a lip or rim 280 of the exhaust port 232 to thereby seal the actuator chamber 212 against venting through the exhaust chamber 204 .
- controlling the pressure in the first I/P chamber 208 to apply a smaller force on the second end 272 than the spring force causes the annular seat member 278 of the valve seat portion 262 to disengage from the lip 280 of the exhaust port 232 causing pressure within the actuator chamber 212 to vent through the exhaust port 232 to the exhaust chamber 204 .
- the relay valve 24 further includes a supply stack 282 having a configuration similar to the exhaust stack 246 .
- the supply stack 282 extends from the supply chamber 206 , through the supply port 234 and the actuator chamber 212 , and to the vented portion 218 of the second I/P chamber 210 through passages 283 , 284 extending from the actuator chamber 212 to the second I/P chamber 210 .
- the supply stack 282 includes a cup-shaped member 286 at a first end 288 thereof; an intermediate valve rod 290 having a first end 292 , a valve seat portion 294 , a narrowed portion 296 extending through the supply port 234 , and a second end 298 ; and an I/P member 300 having a disc-shaped portion 302 and a rod portion 304 at a second end 306 thereof.
- the first end 292 of the intermediate valve rod 290 is configured to mount or couple to the cup-shaped member 286 , such as by extending into a cavity 308 thereof, and the second end 298 engages the rod portion 304 of the I/P member 300 through the I/P diaphragm 214 .
- the supply stack 282 engages a second spring 310 with the first end 288 thereof. So configured, the second spring 310 applies a force on the first end 288 of the supply stack 282 and the I/P diaphragm 214 , due to pressure in the second I/P chamber 210 , provides a counter force to the second end 306 thereof.
- controlling the pressure in the second I/P chamber 210 to apply a smaller force on the second end 306 than the spring force causes an annular seat member 312 of the valve seat portion 294 to engage a lip or rim 314 of the supply port 234 to thereby seal the actuator chamber 212 against a supply of pressurized gas from the supply chamber 206 .
- controlling the pressure in the second I/P chamber 210 to apply a larger force on the second end 306 than the spring force causes the annular seat member 312 of the valve seat portion 294 to disengage from the lip 314 of the supply port 234 causing pressurized air from the supply chamber 206 to enter the actuator chamber 212 through the supply port 234 .
- a force diagram for the exhaust stack 246 is shown in FIG. 5 .
- a force on the valve seat portion 262 is provided by pressure in the actuator chamber 212 . Because the pressure within the actuator chamber 212 can be variable, this force can vary the start point pressures for shifting the exhaust stack 246 .
- the areas for the exhaust port 232 and the first portion 239 of the actuator diaphragm 216 can be generally equal so that the resulting forces cancel one another out.
- a force equation showing this relationship for the actuator exhaust stack 246 is as follows:
- a 1 is the area of the first portion 243 of the I/P diaphragm 214
- P i is the pressure supplied by the first I/P converter 20 a
- a 2 is the area of the first portion 239 of the actuator diaphragm 216
- P a is the pressure in the actuator chamber 212
- a 3 is the area of the exhaust port 232
- F spring is the force of the first spring 276 .
- the start point pressure required from the first I/P converter 20 a is independent of the pressure in the actuator chamber 206 .
- the start point pressure to exhaust the actuator 1 can be a consistent, known quantity unlike the variable start point pressures of conventional relay valves subject to the oftentimes fluctuating pressures in the actuator.
- this configuration provides consistent deadtime for the operation of the system.
- a force diagram for the supply stack 282 is shown in FIG. 6 .
- a force on the valve seat portion 294 is provided by pressure in the actuator chamber 212 .
- the pressure within the actuator chamber 212 can be variable, this force can vary the start point pressures for shifting the supply stack 282 .
- the areas for the supply port 234 and the second portion 241 of the actuator diaphragm 216 can be generally equal so that the resulting forces cancel one another out.
- a force equation showing this relationship for the supply stack 282 is as follows:
- a 4 is the area of the second portion 245 I/P diaphragm 214
- P i is the pressure supplied by the second I/P converter 20 b
- a 5 is the area of the second portion 241 of the actuator diaphragm 216
- P a is the pressure in the actuator chamber 212
- a 6 is the area of the supply port 234
- P s is the pressure in the supply chamber 206
- F spring is the force of the second spring 310 .
- the start point pressure required from the second I/P converter 20 b is independent of the pressure in the actuator chamber 206 .
- the force equation is dependent on the pressure in the supply chamber 206 .
- the pressure in the supply chamber 206 is a known, consistent value. Accordingly, in these cases, the pressure in the supply chamber 206 would have substantially no variable impact on the equation.
- the start point pressure can be a consistent, known quantity unlike the variable start point pressures of conventional relay valves subject to the oftentimes fluctuating pressures in the actuator.
- this configuration provides consistent deadtime for the operation of the system.
- the relay valve 24 ′ includes many of the same components and features as the above relay valve 24 . Accordingly, only the differences will be described herein with similar components denoted with a prime.
- the housing 202 ′ of this form includes a sixth portion 318 that defines spring chambers 320 , 322 for the first and second springs 276 ′, 310 ′, respectively.
- the spring chambers 320 , 322 are open to atmosphere with vents 324 .
- the relay valve 24 ′ includes a supply diaphragm 326 captured between the first and sixth portions 222 ′, 318 of the housing 202 ′.
- First and second portions 328 , 330 of the supply diaphragm 326 extend across the openings between the spring chambers 320 , 322 and the exhaust chamber 204 ′ and supply chamber 206 ′, respectively.
- the exhaust and supply stacks 246 ′, 282 ′ can include cup-shaped members 332 having cavities 334 with openings at the first ends 254 ′, 288 ′ thereof.
- the cavities 334 can be sized to receive the first and second springs 276 ′, 310 ′ therein.
- the cup-shaped members 332 abut the first ends 258 ′, 292 ′ of the intermediate valve rods 256 ′, 290 ′ on either side of the supply diaphragm 326 .
- the components of the exhaust and supply stacks 246 ′, 282 ′ can be secured together through the diaphragms 214 ′, 216 ′, 326 . More specifically, threaded fasteners 336 can be inserted into threaded chambers 338 extending from the first ends 254 ′, 288 ′ of the exhaust and supply stacks 246 ′, 282 ′ through the cup-shaped members 332 to the intermediate valve rods 256 ′, 290 ′ thereof.
- threaded fasteners 340 can be inserted into threaded chambers 342 extending from the second ends 264 ′, 298 ′ of the exhaust and supply stacks 246 ′, 282 ′ through the I/P members 266 ′, 300 ′ and into the intermediate valve rods 256 ′, 290 ′ thereof.
- a force diagram for the exhaust stack 246 ′ of this form is the same as that shown in FIG. 5 .
- a force diagram for the supply stack 282 ′ of this form is shown in FIG. 8 .
- the force diagram for this form includes the force provided by the second portion 330 of the supply diaphragm 326 . Because the pressure within the actuator and supply chambers 212 ′, 206 ′ can be variable, these forces can vary the start point pressures for shifting the supply stack 282 ′.
- the areas for the supply port 234 , the second portion 241 ′ of the actuator diaphragm 216 ′, and the second portion 330 of the supply diaphragm 326 can be generally equal so that the resulting forces cancel one another out.
- a force equation showing this relationship for the supply stack 282 ′ in this form including the supply diaphragm 326 is as follows:
- a 4 is the area of the second portion 245 ′ of the I/P diaphragm 214 ′
- P i is the pressure supplied by the second I/P converter 20 b
- a 5 is the area of the second portion 241 ′ of the actuator diaphragm 216 ′
- P a is the pressure in the actuator chamber 212 ′
- a 6 is the area of the supply port 234 ′
- P s is the pressure in the supply chamber 206
- a 7 is the area of the second portion 330 of the supply diaphragm 326
- F spring is the force of the second spring 310 .
- the start point pressure required from the second I/P converter 20 b is independent of the pressure in the supply chamber 206 and the actuator chamber 212 ′.
- the start point pressure to supply the actuator 1 can be a consistent, known quantity unlike the variable start point pressures of conventional relay valves subject to the oftentimes fluctuating pressures in the actuator chamber 212 and, if applicable, the supply chamber 206 .
- this configuration provides consistent deadtime for the operation of the system.
- housings are described herein having multi-part constructions, portions thereof can be combined as desired.
- single diaphragms are shown with portions thereof coupled to the exhaust and supply stacks, individual diaphragms can be provided for each stack.
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Abstract
Description
- This application claims the benefit of U.S. Provisional Application No. 62/565,960, filed Sep. 29, 2017, which is hereby incorporated by reference herein in its entirety.
- The present disclosure generally relates to pneumatic valves and, more particularly, to pneumatic relay valves.
- Relay valves can be utilized in systems to receive an air mass flow, such as from an I/P converter, and, in response, output a larger air mass flow to an actuator. This type of relay valve can have an inherent deadtime during operation that corresponds to the time when the I/P converter is first operated and when the larger air mass flow beings to flow out of the relay valve. Some actuators require accurate pulses of air out of the relay valve and the inherent deadtime of the system can influence the accuracy of the pluses of air. If the deadtime is not consistent, fine control movements can become erratic.
- One source of variation in the deadtime can come from the areas of the exhaust and supply ports within the relay valve and changes in pressure from the actuator and/or supply. The pressure(s), in combination with the areas, apply forces on the valve seats sealing the exhaust and/or supply ports. If these values change due to fluctuating pressures, a different pressure is required from the I/P converter to open the relay valve, which results in a change of deadtime.
- In some embodiments, a relay valve is described herein that includes a housing with an exhaust chamber, a supply chamber coupled to a supply, an actuator chamber coupled to an actuator, an exhaust port connecting the exhaust chamber to the actuator chamber, a supply port connecting the supply chamber to the actuator chamber, and an I/P chamber coupled to an I/P converter. The relay valve further includes a stack having a first end, a second end, and a valve seat portion where the stack is configured to be shifted within the housing to thereby control opening and closing of one of the exhaust port or supply port with the valve seat portion thereof. A spring of the relay valve is configured to apply a force on the first end of the stack, while an I/P diaphragm mounted within the housing to extend across the I/P chamber is configured to apply a force on the second end of the stack based on pressure provided by the I/P converter. The relay valve further includes an actuator diaphragm mounted within the housing and coupled to the stack where the actuator diaphragm is disposed on an opposite side of the actuator chamber as the one of the exhaust port or supply port and wherein an area of the actuator diaphragm is generally equal to an area of the one of the exhaust port or supply port such that forces acting on the stack due to pressure within the actuator chamber acting on the valve seat portion and the actuator diaphragm cancel one another out.
- In some approaches, the stack can be a supply stack that is configured to be shifted within the housing to thereby control opening and closing of the supply port with the valve seat portion thereof. These approaches can further include providing a supply diaphragm mounted within the housing and coupled to the supply stack. where the supply diaphragm is disposed on an opposite side of the supply chamber as the supply port, and where an area of the supply diaphragm is generally equal to an area of the supply port such that forces acting on the supply stack due to pressure within the actuator chamber acting on the valve seat portion and the actuator diaphragm cancel one another out.
- In other approaches, the stack can be an exhaust stack that is configured to be shifted within the housing to thereby control opening and closing of the exhaust port with the valve seat portion thereof. These approaches can further include providing a supply stack having a first end, a second end, and a valve seat portion where the supply stack is configured to be shifted within the housing to thereby control opening and closing of the supply port with the valve seat portion thereof. With this configuration, the actuator diaphragm can be a first actuator diaphragm, the I/P diaphragm can be a first I/P diaphragm, the spring can be a first spring; the I/P chamber can be an I/P exhaust chamber; and the housing further includes an I/P supply chamber coupled to a supply I/P converter, where the relay valve further includes a second spring configured to apply a force on the first end of the supply stack, a second I/P diaphragm mounted within the housing to extend across the supply I/P chamber, the second I/P diaphragm configured to apply a force on the second end of the supply stack based on pressure provided by the supply I/P converter, and a second actuator diaphragm mounted within the housing and coupled to the supply stack, the second actuator diaphragm disposed on an opposite side of the actuator chamber as the supply port.
- In several aspects, the stack can include an I/P member disposed within the I/P chamber of the housing and a valve rod member having a first end, a second end, and the valve seat portion, where the second end of the valve rod and the I/P member engage one another on either side of the I/P diaphragm.
- In some embodiments, a relay valve is described herein that includes a housing with an exhaust chamber, a supply chamber coupled to a supply, an actuator chamber coupled to an actuator, an exhaust port connecting the exhaust chamber to the actuator chamber, and a supply port connecting the supply chamber to the actuator chamber. The relay valve further includes an exhaust stack having a valve seat portion and being configured to be shifted within the housing to thereby control opening and closing of the exhaust port with the valve seat portion thereof, and a supply stack having a valve seat portion and being configured to be shifted within the housing to thereby control opening and closing of the supply port with the valve seat portion thereof. A first actuator diaphragm of the relay valve is mounted within the housing and coupled to the exhaust stack. The first actuator diaphragm is disposed on an opposite side of the actuator chamber as the exhaust port and an area of the first actuator diaphragm is generally equal to an area of the exhaust port such that forces acting on the exhaust stack due to pressure within the actuator chamber acting on the valve seat portion and the first actuator diaphragm cancel one another out. A second actuator diaphragm of the relay valve is mounted within the housing and coupled to the supply stack. The second actuator diaphragm is disposed on an opposite side of the actuator chamber as the supply port and an area of the second actuator diaphragm is generally equal to an area of the supply port such that forces acting on the supply stack due to pressure within the actuator chamber acting on the valve seat portion and the second actuator diaphragm cancel one another out.
- In some aspects, the first actuator diaphragm and the second actuator diaphragm are portions of a single diaphragm. In other aspects, the relay valve can further include a supply diaphragm mounted within the housing and coupled to the supply stack where the supply diaphragm is disposed on an opposite side of the supply chamber as the supply port and an area of the supply diaphragm is generally equal to an area of the supply port such that forces acting on the supply stack due to pressure within the supply chamber acting on the valve seat portion and the supply diaphragm cancel one another out.
- By several approaches, the housing can include first and second I/P chambers coupled to first and second I/P converters, second ends of the exhaust and supply stacks being disposed within the first and second I/P chambers. The relay valve can further include an I/P diaphragm that includes first and second portions extending across the first and second I/P chambers where the first and second portions are configured to apply a force on the second ends of the exhaust and supply stacks, respectively, based on pressure provided by the respective I/P converter. The relay valve can further include a first spring disposed within the housing and configured to apply a force on the first end of the exhaust stack and a second spring disposed within the housing and configured to apply a force on the first end of the supply stack.
- In some embodiments, any of the relay valves described herein can be incorporated into a system that includes first and second I/P converters coupled to the relay valve and an actuator coupled to the relay valve. In further embodiments, the system can further include a controller coupled to the first and second I/P converters and configured to receive feedback from the actuator.
- In several embodiments, a method for operating a relay valve is described herein where the relay valve includes a housing including an exhaust chamber, a supply chamber coupled to a supply, an actuator chamber coupled to an actuator, an exhaust port connecting the exhaust chamber to the actuator chamber, a supply port connecting the supply chamber to the actuator chamber, and an I/P chamber coupled to an I/P converter. The method includes applying a first force on a first end of a stack disposed within the housing and configured to be shifted therein to thereby control opening and closing of the exhaust port or supply port with a valve seat portion thereof, applying a second force on the valve seat portion of the stack based on pressure within the actuator chamber, applying a third force on the stack having a magnitude generally equal to the second force in an opposite direction thereof with an actuator diaphragm disposed across a portion of the actuator chamber to thereby negate the impact of the second force on the stack, receiving an input pressure from the I/P converter in the I/P chamber, and applying a fourth force on a second end of the stack with an I/P diaphragm disposed across the I/P chamber based on the input pressure to thereby control shifting of the stack.
- By some approaches, the stack is a supply stack configured to be shifted within the housing to thereby control opening and closing of the supply port with the valve seat portion thereof. In these approaches, the method can further include applying a fifth force on the valve seat portion of the supply stack based on pressure within the supply chamber and applying a sixth force on the supply stack having a magnitude generally equal to the fifth force in an opposite direction thereof with a supply diaphragm disposed across a portion of the supply chamber to thereby negate the impact of the fifth force on the supply stack.
- By other approaches, the stack is an exhaust stack configured to be shifted within the housing to thereby control opening and closing of the exhaust port with the valve seat portion thereof. In these approaches, the I/P chamber can be a first I/P chamber, the actuator diaphragm can be a first actuator diaphragm, and the housing can further includes a second I/P chamber coupled to a second I/P converter. With this configuration, the method can further include applying a first force on a first end of a supply stack disposed within the housing and configured to be shifted therein to thereby control opening and closing of the supply port with a valve seat portion thereof, applying a second force on the valve seat portion of the supply stack based on pressure within the actuator chamber, applying a third force on the supply stack having a magnitude generally equal to the second force in an opposite direction thereof with a second actuator diaphragm disposed across a portion of the actuator chamber to thereby negate the impact of the second force on the supply stack, receiving an input pressure from the second I/P converter in the second I/P chamber, and applying a fourth force on a second end of the supply stack with a second I/P diaphragm disposed across the second I/P chamber based on the input pressure from the second I/P converter to thereby control shifting of the supply stack.
- The above needs are at least partially met through provision of the methods, relay valves, systems, and components thereof described in the following detailed description, particularly when studied in conjunction with the drawings, wherein:
-
FIG. 1 is a block diagram of an example implementation of a valve positioning system, including a spring return pneumatic actuator, in accordance with various embodiments of the present disclosure; -
FIG. 2 is a block diagram of an alternative implementation of the valve positioning system ofFIG. 1 , including a double acting pneumatic actuator, in accordance with various embodiments of the present disclosure; -
FIG. 3 is a focused block diagram including a pneumatic relay valve in accordance with various embodiments of the present disclosure; -
FIG. 4 is a first embodiment of a relay valve in accordance with various embodiments of the present disclosure; -
FIG. 5 is a force diagram for an exhaust stack of the relay valve ofFIG. 4 in accordance with various embodiments of the present disclosure; -
FIG. 6 is a force diagram for a supply stack of the relay valve ofFIG. 4 in accordance with various embodiments of the present disclosure; -
FIG. 7 is a second embodiment of a relay valve in accordance with various embodiments of the present disclosure; and -
FIG. 8 is a force diagram for a supply stack of the relay valve ofFIG. 7 in accordance with various embodiments of the present disclosure. - Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.
- A relay valve configured according to the various embodiments as described herein advantageously provides consistent, reliable start point pressures for both supply and exhaust functionalities. To achieve this, the relay valves described herein utilize a plurality of diaphragms to neutralize any variable forces due to pressure in an actuator and, optionally, a supply connected to the relay valve.
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FIG. 1 is a block diagram of an example implementation of a valve positioning system comprising anactuator 1 for opening and closing a process control valve (PCV). In the implementation ofFIG. 1 , theactuator 1 may be a spring return pneumatic actuator. - In some implementations, the
positioner 10 may configured to include some or all of the advanced functionality of a digital valve controller (DVC), thoughFIG. 1 does not illustrate this functionality. Theactuator 1 may comprise apneumatic chamber 2 and a spring 3, which may be separated by apiston 4. Addition of pneumatic pressure to thepneumatic chamber 2 may cause movement of thepiston 4, which may in turn cause movement of astem 5 connected to thepiston 4. Conversely, removal of pneumatic pressure from thepneumatic chamber 2 may cause opposite movement of thepiston 4 and thestem 5. Collectively, the movement of the stem 5 (e.g., linear or angular displacement of the stem 5) may open or close the process control valve through which process fluid may flow. The process control valve may control fluid flow within a process control system, such as a chemical or other process control plant. - An supply/
exhaust port 6 may supply air or other control fluid to thepneumatic chamber 2, and/or conversely, may exhaust control fluid from thepneumatic chamber 2. In some embodiments, the supply/exhaust port 6 may comprise separate ports for supply and exhaust of control fluid to thepneumatic chamber 2. Addition or removal of control fluid to thepneumatic chamber 2 may increase or decrease, respectively, the pneumatic pressure in thepneumatic chamber 2, consequently causing a change in actuator position and thus a change in process fluid flow through the process fluid valve. - In some implementations, the
actuator 1 may additionally include a fail-safe spring (not pictured) in thepneumatic chamber 2. Such a spring may place an actuator at one limit of the actuators range when, for example, thechamber 2 depressurizes due to a control fluid leak. - In some implementations, a mechanism in an
alternative actuator 1 may translate the linear motion of thepiston 4 into rotary motion of thestem 5 by means of rack and pinion, scotch yoke, or another mechanism. - A
position sensor 11 may be configured to detect the position of theactuator 1, for example, by detecting linear displacement of thestem 5. In implementations with an alternative rotary actuator, analternative position sensor 11 may be configured to measure angular displacement of some portion of the alternative rotary actuator. Apressure sensor 14 may be configured to detect an amount of pneumatic pressure in thepneumatic chamber 2. In some implementations, thepressure sensor 14 may be located at an outlet port of thechamber 2. Additionally or alternatively, thepressure sensor 14 may be integrated into the body of thepositioner 10, and connected tochamber 2 via a pneumatic line. In any case, theposition sensor 11 andpressure sensor 14 may be communicatively connected to acontroller 16 to provide feedback of observed actuator position and pressure to thecontroller 16. - The
controller 16 may include wired and/or wireless connections, circuitry for communications and signal processing, non-transient memory and/or a human-machine interface. In an example implementation, thecontroller 16 includes processing software such as a microprocessor and a computer-readable memory to store software instructions. Thecontroller 16 may be configured to receive position feedback from theposition sensor 11, and/or pressure feedback from thepressure sensor 14. Generally, thecontroller 16 may be configured to use the received feedback to execute a control algorithm to control position of theactuator 1. In some implementations, the controller may comprise one or more microprocessors. In other implementations, thecontroller 16 may comprise field programmable gate arrays (FPGAs) or analog circuits. Thecontroller 16 may be configured to execute the control algorithm (e.g., a Multiple Input Multiple Output (MIMO) control algorithm) to output electrical control signals to respective current-to-pressure (I/P) transducers 20 a and 20 b for generating pneumatic signals for theactuator 1. Thecontroller 16 may additionally be configured to compute other signals, such as diagnostic information about the positioner and the actuator. Thepositioner 10 may additionally comprise aninterface 18 communicatively coupled to thecontroller 16. In some embodiments, theinterface 18 may communicate actuator control constraints, process variable set points, and/or other information, that may be defined by a human operator and/or a control algorithm. - The
controller 16 may output electrical signals for controlling theactuator 1, the electrical signals transmitted to the I/P transducers pneumatic relay 24 which may amplify the flow rates specified via thetransducers FIG. 3 ). Electrical signals transmitted to the I/P transducer 20 a may correspond to the supply of pressurized control fluid to thepneumatic chamber 2, while signals transmitted to thetransducer 20 b may correspond to exhaust of control fluid from thechamber 2. Thepneumatic relay 24 may amplify the pneumatic signals generated via thetransducers pneumatic chamber 2 via the supply/exhaust port 6. -
FIG. 2 is a block diagram of an alternative implementation of the valve positioning system ofFIG. 1 . In theFIG. 2 implementation, a double-actingpneumatic actuator 1 replaces the springreturn pneumatic actuator 1 ofFIG. 1 . The double-actingpneumatic actuator 1 includes an upperpneumatic chamber 2 and a lowerpneumatic chamber 7. The valve positioning system ofFIG. 2 may operate similarly to the system described with regard toFIG. 1 , apart the differences described herein. - The upper
pneumatic chamber 2 and lowerpneumatic chamber 7 may be separated by thepiston 4. A pressure differential between thechambers piston 4, which in turn may cause movement of thestem 5, thus opening or closing the process control valve and affecting process fluid flow. - Supply/
exhaust ports upper chamber 2 andlower chamber 7, respectively. As the amount of control fluid changes in either or both of thechambers chambers piston 4 andstem 5 to partially or fully open or close the control valve. In some embodiments, either or both of the supply/exhaust ports respective chambers - In some implementations, the double-acting
actuator 1 may include a spring (not shown) in one or both of thechambers chambers - A pair of
pressure sensors pneumatic chamber 2 and lowerpneumatic chamber 7, respectively. In some implementations, thepressure sensors respective chambers pressure sensors positioner 10, and connected to therespective chambers position sensor 11 andpressure sensors controller 16 to provide feedback of observed actuator position and pressure to thecontroller 16. - The
controller 16 may be a similar controller to that described regarding theFIG. 1 implementation. Thecontroller 16 may be configured to execute a control algorithm (e.g., a MIMO control algorithm) to output electrical control signals to I/P transducers 20 a-20 d. Electrical signals transmitted to the I/P transducer 20 a may correspond to the supply of pressurized control fluid to the upperpneumatic chamber 2, while signals transmitted to thetransducer 20 b may correspond to exhaust of control fluid from theupper chamber 2. Electrical signals transmitted to the I/P transducer 20 c may correspond to the supply of pressurized control fluid to the lowerpneumatic chamber 7, while signals transmitted to thetransducer 20 d may correspond to exhaust of control fluid from thelower chamber 7. Apneumatic relay 24 may amplify the pneumatic signals generated via thetransducers pneumatic chamber 2 via the supply/exhaust port 6 a. Similarly, apneumatic relay 24 may amplify the pneumatic signals generated via thetransducers pneumatic chamber 7 via the supply/exhaust port 6 b. -
FIG. 3 is a more focused block diagram including apneumatic relay 24 in accordance with various embodiments of the present disclosure. The components illustrated inFIG. 3 may be included, for example, in the valve positioning systems described with regard toFIG. 1 andFIG. 2 . - An electrical control signal (current 0 may be supplied to the I/
P transducer 20. The I/P transducer 20 receives the control signal and outputs a small air mass flow (mi/p) to thepneumatic relay 24. This small air mass flow may pressurize a diaphragm chamber in therelay 24, which opens a relay valve in therelay 24. When the relay valve is opened, a larger air mass flow (mrelay) may flow from therelay 24 to the actuator 1 (e.g., via a supply/exhaust port of theactuator 1 to pressurize or depressurize a pneumatic chamber of theactuator 1. - A deadtime may correspond to a period of time that is present between a first time at which current i is first supplied to the I/
P transducer 20, and a second, subsequent time at which the air mass flow mrelay begins to flow out of thepneumatic relay 24. Inconsistent deadtime in a valve positioner may cause fine control movements (e.g., actuator position movements) to become erratic. Inconsistency in deadtime may be caused, for example, via an unbalanced area of a supply port and exhaust port of the pneumatic relay, as will be described with regard toFIGS. 4-8 . - With reference to
FIG. 4 , arelay valve 24 in a first form is shown. Therelay valve 24 includes ahousing 202 having anexhaust chamber 204, asupply chamber 206, a first I/P chamber 208, a second I/P chamber 210, and anactuator chamber 212. Therelay valve 24 further includes an I/P diaphragm 214 and anactuator diaphragm 216. The I/P diaphragm 214 divides the first and second I/P chambers portion 218 and apressurized portion 220. - In the illustrated form, the
housing 202 has a five piece, multi-part construction including first 222, second 224, third 226, fourth 228, and fifth 230 portions. The first andsecond portions supply chambers third portions actuator chamber 212 therebetween and thesecond portion 224 includes anexhaust port 232 connecting theactuator chamber 212 to theexhaust chamber 204 and asupply port 234 connecting theactuator chamber 212 to thesupply chamber 206. Theactuator diaphragm 216 is disposed between the third andfourth portions actuator chamber 212. The third andfourth portions actuator diaphragm chambers second portions actuator diaphragm 216 extending thereacross with pressure from the actuator on one side thereof and atmosphere on the other side thereof. Thechambers second portions actuator diaphragm 216 are generally circular. Of course, all actuators/actuator portions described herein can be configured as commonly understood with excess material to allow the diaphragm/diaphragm portion to flex in either direction. The fourth andfifth portions P chambers P diaphragm 214 therebetween. First andsecond portions P chambers portions 218 of the first and second I/P chambers fourth portion 230 and the I/P diaphragm 214 and thepressurized portions 220 are defined by thefifth portion 230 and the I/P diaphragm 214. - The
supply chamber 206 is coupled to and receives pressurized gas from asupply 233 via a suitable connection/port 236. Theexhaust chamber 204 includes avent 238 open to atmosphere. The ventedportions 218 of the first and second I/P chambers vents 240 open to atmosphere and thepressurized portions 220 thereof are coupled to first and second I/P converters ports 242, to thereby receive pressurized gas and exhaust gas. If desired, thehousing 202 can include cavities or mounts 244 to receive the first and second I/P converters - As shown in
FIG. 4 , therelay valve 24 further includes anexhaust stack 246 that extends from theexhaust chamber 204, through theexhaust port 232 and theactuator chamber 212, and to the ventedportion 218 of the first I/P chamber 208 throughpassages actuator chamber 212 to the first I/P chamber 208. Theexhaust stack 246 includes a cup-shapedmember 252 at afirst end 254 thereof; anintermediate valve rod 256 having afirst end 258, a narrowedportion 260 extending through theexhaust port 232, avalve seat portion 262, and asecond end 264; and an I/P member 266 having a disc-shapedportion 268 and arod portion 270 at asecond end 272 thereof. Thefirst end 254 of theintermediate valve rod 252 is configured to mount or couple to the cup-shapedmember 248, such as by extending into acavity 274 thereof, and thesecond end 264 engages therod portion 270 of the I/P member 266 through the I/P diaphragm 214. - The
exhaust stack 246 engages afirst spring 276 with thefirst end 254 thereof. So configured, thefirst spring 276 applies a force on thefirst end 254 of theexhaust stack 246. Thefirst portion 243 of the I/P diaphragm 214, due to pressure in the first I/P chamber 208, provides a counter force to thesecond end 272 thereof. By a first approach, controlling the pressure in the I/P chamber 208 to apply a larger force on thesecond end 272 than the spring force causes anannular seat member 278 of thevalve seat portion 262 to engage a lip or rim 280 of theexhaust port 232 to thereby seal theactuator chamber 212 against venting through theexhaust chamber 204. By a similar, second approach, controlling the pressure in the first I/P chamber 208 to apply a smaller force on thesecond end 272 than the spring force causes theannular seat member 278 of thevalve seat portion 262 to disengage from thelip 280 of theexhaust port 232 causing pressure within theactuator chamber 212 to vent through theexhaust port 232 to theexhaust chamber 204. - As shown in
FIG. 4 , therelay valve 24 further includes asupply stack 282 having a configuration similar to theexhaust stack 246. Thesupply stack 282 extends from thesupply chamber 206, through thesupply port 234 and theactuator chamber 212, and to the ventedportion 218 of the second I/P chamber 210 throughpassages actuator chamber 212 to the second I/P chamber 210. Thesupply stack 282 includes a cup-shapedmember 286 at afirst end 288 thereof; anintermediate valve rod 290 having afirst end 292, avalve seat portion 294, a narrowedportion 296 extending through thesupply port 234, and asecond end 298; and an I/P member 300 having a disc-shapedportion 302 and arod portion 304 at asecond end 306 thereof. Thefirst end 292 of theintermediate valve rod 290 is configured to mount or couple to the cup-shapedmember 286, such as by extending into acavity 308 thereof, and thesecond end 298 engages therod portion 304 of the I/P member 300 through the I/P diaphragm 214. - The
supply stack 282 engages asecond spring 310 with thefirst end 288 thereof. So configured, thesecond spring 310 applies a force on thefirst end 288 of thesupply stack 282 and the I/P diaphragm 214, due to pressure in the second I/P chamber 210, provides a counter force to thesecond end 306 thereof. By a first approach, controlling the pressure in the second I/P chamber 210 to apply a smaller force on thesecond end 306 than the spring force causes anannular seat member 312 of thevalve seat portion 294 to engage a lip or rim 314 of thesupply port 234 to thereby seal theactuator chamber 212 against a supply of pressurized gas from thesupply chamber 206. By a similar, second approach, controlling the pressure in the second I/P chamber 210 to apply a larger force on thesecond end 306 than the spring force causes theannular seat member 312 of thevalve seat portion 294 to disengage from thelip 314 of thesupply port 234 causing pressurized air from thesupply chamber 206 to enter theactuator chamber 212 through thesupply port 234. - A force diagram for the
exhaust stack 246 is shown inFIG. 5 . As set forth above, in addition to the forces provided by thefirst spring 276 and thefirst portion 243 of the I/P diaphragm 214, a force on thevalve seat portion 262 is provided by pressure in theactuator chamber 212. Because the pressure within theactuator chamber 212 can be variable, this force can vary the start point pressures for shifting theexhaust stack 246. Advantageously, the areas for theexhaust port 232 and thefirst portion 239 of theactuator diaphragm 216 can be generally equal so that the resulting forces cancel one another out. - A force equation showing this relationship for the
actuator exhaust stack 246 is as follows: -
ΣF=0=−A 1 P i +A 2 P a −A 3 P a +F spring - Where A1 is the area of the
first portion 243 of the I/P diaphragm 214, Pi is the pressure supplied by the first I/P converter 20 a, A2 is the area of thefirst portion 239 of theactuator diaphragm 216, Pa is the pressure in theactuator chamber 212, A3 is the area of theexhaust port 232, and Fspring is the force of thefirst spring 276. - Manipulating the equation to reflect the value of the pressure supplied by the first I/
P converter 20 a, the equation becomes: -
- If A2=A3, the equation simplifies to:
-
- Accordingly, by making the areas of the
first portion 239 of theactuator diaphragm 216 and theexhaust port 232 equal, the start point pressure required from the first I/P converter 20 a is independent of the pressure in theactuator chamber 206. This means that the start point pressure to exhaust theactuator 1 can be a consistent, known quantity unlike the variable start point pressures of conventional relay valves subject to the oftentimes fluctuating pressures in the actuator. Moreover, this configuration provides consistent deadtime for the operation of the system. - A force diagram for the
supply stack 282 is shown inFIG. 6 . As set forth above, in addition to the forces provided by thesecond spring 310 and thesecond portion 245 of the I/P diaphragm 214, a force on thevalve seat portion 294 is provided by pressure in theactuator chamber 212. Because the pressure within theactuator chamber 212 can be variable, this force can vary the start point pressures for shifting thesupply stack 282. Advantageously, the areas for thesupply port 234 and thesecond portion 241 of theactuator diaphragm 216 can be generally equal so that the resulting forces cancel one another out. - A force equation showing this relationship for the
supply stack 282, is as follows: -
ΣF=0=−A 4 P i +A 5 P a −A 6 P a +A 6 P s +F spring - Where A4 is the area of the second portion 245 I/
P diaphragm 214, Pi is the pressure supplied by the second I/P converter 20 b, A5 is the area of thesecond portion 241 of theactuator diaphragm 216, Pa is the pressure in theactuator chamber 212, A6 is the area of thesupply port 234, Ps is the pressure in thesupply chamber 206, and Fspring is the force of thesecond spring 310. - Manipulating the equation to reflect the value of the pressure supplied by the second I/
P converter 20 b, the equation becomes: -
- If A5=A6, the equation simplifies to:
-
- Accordingly, by making the areas of the
second portion 241 of theactuator diaphragm 216 equal to thesupply port 234, the start point pressure required from the second I/P converter 20 b is independent of the pressure in theactuator chamber 206. The force equation is dependent on the pressure in thesupply chamber 206. In many cases, however, the pressure in thesupply chamber 206 is a known, consistent value. Accordingly, in these cases, the pressure in thesupply chamber 206 would have substantially no variable impact on the equation. This means that the start point pressure can be a consistent, known quantity unlike the variable start point pressures of conventional relay valves subject to the oftentimes fluctuating pressures in the actuator. Moreover, this configuration provides consistent deadtime for the operation of the system. - With reference to
FIG. 7 , arelay valve 24′ of a second form is shown. Therelay valve 24′ includes many of the same components and features as theabove relay valve 24. Accordingly, only the differences will be described herein with similar components denoted with a prime. - The
housing 202′ of this form includes asixth portion 318 that definesspring chambers second springs 276′, 310′, respectively. Thespring chambers vents 324. Further, therelay valve 24′ includes asupply diaphragm 326 captured between the first andsixth portions 222′, 318 of thehousing 202′. First andsecond portions supply diaphragm 326 extend across the openings between thespring chambers exhaust chamber 204′ andsupply chamber 206′, respectively. - Further, as shown in
FIG. 7 , the exhaust andsupply stacks 246′, 282′ can include cup-shapedmembers 332 havingcavities 334 with openings at the first ends 254′, 288′ thereof. Thecavities 334 can be sized to receive the first andsecond springs 276′, 310′ therein. The cup-shapedmembers 332 abut the first ends 258′, 292′ of theintermediate valve rods 256′, 290′ on either side of thesupply diaphragm 326. - Moreover, the components of the exhaust and
supply stacks 246′, 282′ can be secured together through thediaphragms 214′, 216′, 326. More specifically, threadedfasteners 336 can be inserted into threadedchambers 338 extending from the first ends 254′, 288′ of the exhaust andsupply stacks 246′, 282′ through the cup-shapedmembers 332 to theintermediate valve rods 256′, 290′ thereof. Similarly, threadedfasteners 340 can be inserted into threadedchambers 342 extending from the second ends 264′, 298′ of the exhaust andsupply stacks 246′, 282′ through the I/P members 266′, 300′ and into theintermediate valve rods 256′, 290′ thereof. - A force diagram for the
exhaust stack 246′ of this form is the same as that shown inFIG. 5 . A force diagram for thesupply stack 282′ of this form is shown inFIG. 8 . As set forth above, in addition to the forces provided by thesecond spring 310′, thesecond portion 245 of the I/P diaphragm 214′, and the force on thevalve seat portion 294′ provided by pressure in theactuator chamber 212′, the force diagram for this form includes the force provided by thesecond portion 330 of thesupply diaphragm 326. Because the pressure within the actuator andsupply chambers 212′, 206′ can be variable, these forces can vary the start point pressures for shifting thesupply stack 282′. Advantageously, the areas for thesupply port 234, thesecond portion 241′ of theactuator diaphragm 216′, and thesecond portion 330 of thesupply diaphragm 326 can be generally equal so that the resulting forces cancel one another out. - A force equation showing this relationship for the
supply stack 282′ in this form including thesupply diaphragm 326 is as follows: -
ΣF=0=−A 4 P i +A 5 P a −A 6 P a +A 6 P s −A 7 P s +F spring - Where A4 is the area of the
second portion 245′ of the I/P diaphragm 214′, Pi is the pressure supplied by the second I/P converter 20 b, A5 is the area of thesecond portion 241′ of theactuator diaphragm 216′, Pa is the pressure in theactuator chamber 212′, A6 is the area of thesupply port 234′, Ps is the pressure in thesupply chamber 206, A7 is the area of thesecond portion 330 of thesupply diaphragm 326, and Fspring is the force of thesecond spring 310. - Manipulating the equation to reflect the value of the pressure supplied by the second I/
P converter 20 b, the equation becomes: -
- If A5=A6 and A6=A7, the equation simplifies to:
-
- Accordingly, by making the areas of the
second portion 241′ of theactuator diaphragm 216′ and thesecond portion 330 of thesupply diaphragm 326 equal to thesupply port 234′, the start point pressure required from the second I/P converter 20 b is independent of the pressure in thesupply chamber 206 and theactuator chamber 212′. This means that the start point pressure to supply theactuator 1 can be a consistent, known quantity unlike the variable start point pressures of conventional relay valves subject to the oftentimes fluctuating pressures in theactuator chamber 212 and, if applicable, thesupply chamber 206. Moreover, this configuration provides consistent deadtime for the operation of the system. - Those skilled in the art will recognize that a wide variety of modifications, alterations, and combinations can be made with respect to the above described embodiments without departing from the scope of the invention, and that such modifications, alterations, and combinations are to be viewed as being within the ambit of the inventive concept. For example, although housings are described herein having multi-part constructions, portions thereof can be combined as desired. Further, although single diaphragms are shown with portions thereof coupled to the exhaust and supply stacks, individual diaphragms can be provided for each stack.
Claims (24)
Priority Applications (1)
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US16/146,379 US10802510B2 (en) | 2017-09-29 | 2018-09-28 | Relay valve and force balancing method |
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US201762565960P | 2017-09-29 | 2017-09-29 | |
US16/146,379 US10802510B2 (en) | 2017-09-29 | 2018-09-28 | Relay valve and force balancing method |
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US20190101943A1 true US20190101943A1 (en) | 2019-04-04 |
US10802510B2 US10802510B2 (en) | 2020-10-13 |
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US16/146,379 Active US10802510B2 (en) | 2017-09-29 | 2018-09-28 | Relay valve and force balancing method |
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US (1) | US10802510B2 (en) |
EP (1) | EP3688317B1 (en) |
CN (2) | CN210050360U (en) |
CA (1) | CA3076749A1 (en) |
RU (1) | RU2020112880A (en) |
WO (1) | WO2019067422A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11236846B1 (en) * | 2019-07-11 | 2022-02-01 | Facebook Technologies, Llc | Fluidic control: using exhaust as a control mechanism |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CA3076749A1 (en) * | 2017-09-29 | 2019-04-04 | Fisher Controls International Llc | Relay valve and force balancing method |
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2018
- 2018-09-25 CA CA3076749A patent/CA3076749A1/en active Pending
- 2018-09-25 RU RU2020112880A patent/RU2020112880A/en unknown
- 2018-09-25 WO PCT/US2018/052601 patent/WO2019067422A1/en unknown
- 2018-09-25 EP EP18786163.8A patent/EP3688317B1/en active Active
- 2018-09-28 US US16/146,379 patent/US10802510B2/en active Active
- 2018-09-29 CN CN201821603507.6U patent/CN210050360U/en active Active
- 2018-09-29 CN CN201811150569.0A patent/CN109578657B/en active Active
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Also Published As
Publication number | Publication date |
---|---|
CN109578657A (en) | 2019-04-05 |
CN109578657B (en) | 2023-05-16 |
CN210050360U (en) | 2020-02-11 |
RU2020112880A (en) | 2021-10-29 |
US10802510B2 (en) | 2020-10-13 |
EP3688317A1 (en) | 2020-08-05 |
WO2019067422A1 (en) | 2019-04-04 |
EP3688317B1 (en) | 2023-05-10 |
CA3076749A1 (en) | 2019-04-04 |
RU2020112880A3 (en) | 2021-11-30 |
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